None.
1. Field of the Invention
The present invention relates generally to the art of vehicle seating and more particularly to the back portion of a vehicle seat. In its most preferred embodiment, the seat of the present invention includes a pelvis support, a pivoting thorax support and a height adjustment system for positioning the pivoting thorax support at the correct height for the seat occupant. In its most preferred embodiment, the vertical height system gives up to 100 mm of adjustment range to correctly position the thorax support for most adults.
2. Description of the Prior Art
A wide variety of comfort controlled vehicle seating systems are well-known and currently in use. Simple systems provide fore and aft adjustability and reclining of the seat back. More sophisticated seating systems add manual or power lumbar supports, vertically adjustable headrests, height and tilt controls for the seat cushion, and the like. Many of the current seats are designed and modeled for a mannequin named xe2x80x9cOSCARxe2x80x9d in the industry and more specifically to the movement of OSCAR about a hip joint center.
Researchers at Michigan State University in the early 1990""s began to look more carefully at actual movements of the body in an automotive vehicle setting and came up with a new modelxe2x80x94xe2x80x9cJOHNxe2x80x9d named after the research sponsor, Johnson Controls, Inc.xe2x80x94and developed relationships between thorax and pelvic movement and the impact on lumbar curvature.
These researchers determined that there is a relationship between these two movements and that a desired curvature for the lumbar area could be created if the thorax area is moved significantly. Instead of having a lumbar support push the lumbar vertebrae forwardly (mechanical, pneumatic, manual, powered, etc.), they found that the thorax area moves in a counter rotation with respect to the pelvis. When the thorax moves forward in this model, the shoulders actually move rearwardly. This work led to the prediction that seat comfort could be enhanced if the thorax could be supported in all positions from the equivalent of JOHN being slumped forwardly on a stool to a position in which JOHN is sitting erect, with a total lumbar curvature of about 50xc2x0. The schematics discussed later in the detailed description portion of this specification illustrate several of these basic research findings.
Despite this theoretical explanation of seating comfort, developments in the 1990""s continued to focus on lumbar support and lumbar height, and several vehicles currently being sold include lumbar supports that go up and down as well as in and out. While seeming to provide some comfort enhancement for vehicle seating occupants, such products ignore the research findings that comfort can, in fact, be enhanced if thorax support is also provided. Several developments in vehicle seating systems will now be discussed to illustrate the current state of this art and the variety of different directions major companies are following to provide a solution to a substantial issue, i.e., occupant comfort over a prolonged period of sitting.
As background, it is well recognized that static seats or those employing baskets, paddles and bladder systems can be used for lumbar support. The latter are all variations on a single principle. Each forces the lumbar region into a lordotic or concave shape with the intent of creating a more erect posture and hence greater comfort. Lumbar paddles and baskets can be manually operated or powered. Lumbar bladders are filled with air using a manual pump or an electrically powered pump to increase the bladder""s volume and the amount of prominence into the back.
Variations on the lumbar support theory of occupant comfort are numerous. For example in U.S. Pat. No. 4,564,235 issued on Jun. 14, 1986 to Hatsutta et al, the lumbar support is split into two parts, and a cam inside the seat controls their positioning. A rotating wheel on the seat is used to rotate the cam to move the top paddle forwardly or rearwardly.
Another attempt at occupant comfort is described in U.S. Pat. No. 5,411,317 issued to Faust et al. on May 2, 1995. An important feature of this seat is a contour vortex located 250-275 mm above the seat surface combined with a rigid pelvic support 150-175 above the seat surface. This seat is static, i.e., the contour vortex and the pelvic support do not move with respect to each other.
Two additional static seats which discuss comfort are known to the present inventors. A so-called xe2x80x9ciliacxe2x80x9d seat has a contour in the pelvic region and an extreme amount of contour in the location of the iliac crests of the pelvis. Their purpose is to support the pelvis and avoid hyperflexion of the lower lumbar joints to eliminate the probability of pain. The second is called a New Generation Ergonomic Seat which features a lumbar support and a seat contour which is designed to provide support from the pelvis (sacrum) to the 10th thoracic vertebrae (located at the bottom of the thorax). This seat simulates a position the body would assume if lying in a bed, a so-called xe2x80x9cneutralxe2x80x9d position with less curvature than would be encountered if the person was standing erect.
Another posture enhancing effort is described in U.S. Pat. No. 5,452,868 issued to Kanigowski on Sep. 26, 1995. This seat uses a gas-spring actuator to provide changes in lumbar prominence. The seat adjustment begins with maximum lumbar prominence, and by depressing a button, the occupant is able to press back into the lumbar support, compressing the gas spring and infinitely varying the amount of prominence.
A seat having a flexible contour to influence posture is described in U.S. Pat. No. 5,026,116 issued to Dal Monte on Jun. 25, 1991. The flexible elements extend vertically with the seat frame, and two transverse, rigid bars control the elements in the upper back and lumbar regions. The contour changes as the bars are moved relative to one another, i.e., when the bar located in the lumbar area moves forwardly to increase lumbar prominence, the bar in the mid-back region moves rearwardly to allow the thorax to move backwards.
Yet a further seat maneuvering system is disclosed in Serber""s U.S. Pat. No. 5,558,399 issued on Sep. 24, 1996. The seat includes a cushion, a lower back support and an upper back support, the latter two being pivotally coupled in the mid-back region. The cushion moves on a pair of rollers in an arc relationship to the mid-back pivot. While the main object of the seat is safety (i.e., anti-submarining), increased comfort is attributed to the seat by the inventor.
U.S. Pat. No. 5,505,520 issued to Frusti, et al. on Apr. 9, 1996 references work by Hubbard et al. at Michigan State University and seems to incorporate some of the motions of xe2x80x9cJOHNxe2x80x9d described above. The seat has pelvis, lumbar and thoracic support, but movement of them is controlled solely by movement of the lumbar support. The other two are connected to it, the thoracic support being pivotally connected to the top of the seat back frame. This allows the shoulders to recline and the lower part of the thorax to be supported. The patent does not describe any vertical movement between the various body supports.
A biomechanically articulating chair has been devised and was built around the movements of the xe2x80x9c2D JOHNxe2x80x9d model. Allegedly it provides improved postural support by supporting the pelvis, thorax, and the lumbar region. The seat articulates as if xe2x80x9cJOHNxe2x80x9d pivots on the ischial tuberosites. The pelvis support pivots just under the ischial tuberosites of the occupant, while the thorax support pivots in the mid-back. The chair is intended to support the occupant through a wide range of spinal curvature and torso recline angles, thereby maintaining geometric compatibility between the height of the occupant and the seat contour to eliminate undesirable pressure distributions on the occupant. This chair is known for use in the office furniture or home fields and is not specifically illustrated for use with motor vehicle seating.
Finally, U.S. Pat. No. 6,082,823 issued to Aumont et al. on Jul. 4, 2000 describes a backrest which includes an upper backrest frame located above a lower backrest frame, the lower edge thereof be coupled to the lower backrest frame using a hinge. Pivoting of the upper portion of the back is permitted, but again there is no vertical height adjustment of the frame.
While several of the above-mentioned seat constructions can enhance occupant comfort, the present inventor believes a substantial improvement over all of them can be provided. Such improvement would be considered an important advance in this art.
A primary feature of the present invention is to overcome the above-noted disadvantages of prior art seating systems by providing a seat that more closely follows the way a seated person moves, thus providing a wider range of seated positions that are available in any currently known seating.
Another feature of the present invention is to provide a seating system which adjusts to a plurality of different seated heights.
A different feature of the present invention is to reduce postural fixity, i.e., the pain in the back which results from sitting too long causing muscle fatigue, reducing creation of waste products in the skeletal system and optimizing the geometry of the vertebrae and giving the diaphragm room to expand leading to the lungs having more breathing room and capacity.
A further feature of the present invention is to provide a seating system which can be readily modified for a variety of different motor vehicle styles and which uses components which are already being used in motor vehicle seats for different purposes.
Another feature of the present invention is its ability to provide the aforementioned features for a substantial majority of people, for example, from the 5% female (height 4 ft., 11 in.) through the 95% male (6 ft., 4 in.)
How these and other features of this invention are accomplished individually, and in various combinations, will be described in the following detailed description of the preferred embodiment, taken in conjunction with the FIGURES. Generally, however, they are accomplished in a biomechanical seating system that follows the motions of the JOHN model, in which on a stool, JOHN moves from a slumped posture to an erect posture rotating about ischial tuberosities (or xe2x80x9cset bonesxe2x80x9d). From the side, this motion looks like a pivot forming in the back of the occupant, located near the bottom of the shoulder blades. The biomechanical seat of the present invention follows such motion by first supporting the movement of the thorax with a thorax support which pivots about the bottom of the shoulder blades, and since the lower thorax has a rigid support to hold it, the shoulders will recline. By simultaneously supporting the pelvis, the linked motion between the pelvis and thorax (in the JOHN model) is continued and the lumbar vertebrae are allowed to move like a link between two rigid structures. In addition, pelvic support is more effective at controlling postural change than lumbar support. The biomechanical seat of the present invention further provides for vertical height adjustment, since the desired thorax pivot point changes depending on occupant stature. A set of seat tracks are illustrated for enabling an adjustment of about 100 mm to cover the desired pivot height range from at least the 5% female to the 95% male. Other ways in which the features of the present invention are accomplished will become apparent to those skilled in the seating art after the present specification has been studied. Such other ways are deemed to fall within the scope of the present invention if they fall within the scope of the claims which follow.